1. Field of the Invention
The present invention relates to network interface devices for Ethernet networks which carry high speed digital signals over unshielded twisted pair cables.
2. Discussion of the Related Art
It is known in the art to provide network interface devices for connecting telephone company lines with subscriber telephone lines and to provide overvoltage protection for the telephone lines. Typical network interface devices are shown in U.S. Pat. No. 5,553,136 issued to Carl H. Meyerhoefer et al on Sep. 3, 1996 (hereafter the “Meyerhoefer '136 patent”), U.S. Pat. No. 4,979,209 issued to Thomas J. Collins et al. on Dec. 18, 1990 (hereafter the “Collins '209 patent”), U.S. Pat. No. 5,450,469 issued to Oliver Parmart et al. on Sep. 12, 1995 and U.S. Pat. No. 5,416,837 issued to Mark P. Cote et al. on May 16, 1995.
It is known in the art to provide network interface devices for connecting coaxial cables. Such network interface devices are shown in the Meyerhoefer '136 patent and in U.S. Pat. No. 5,394,466 issued to Pina Schneider et al on Feb. 28, 1995 (hereafter the “Schneider '466 patent”). It is also known to provide overvoltage protection for coaxial cables. Coaxial cable overvoltage protection devices are shown, for example, in U.S. Pat. No. 4,616,155 issued to Francois Guichard on Oct. 7, 1986 and in U.S. Pat. No. 5,566,056 issued to Nisar A. Chaudhry on Oct. 15, 1996 (hereafter the “Chaudhry '056 patent”).
The June 1997 issue of Cabling Business contains an article entitled “Cabling For Ethernet (10 Mb), Fast Ethernet (100 Mb) And Gigabit Ethernet” (pages 74–75). It identifies IEEE specification 802.3i (also known as 10BASE-T) and IEEE specification 802.3u (also known as 100BASE-TX) and states that 10BASE-T Ethernet networks handle 10 megabits per second (Mbps) while 100BASE-TX Fast Ethernet networks handle 100 Mbps.
Both 10BASE-T Ethernet and 100BASE-TX Fast Ethernet can be transmitted over unshielded twisted pair (“UTP”) wires. One twisted pair is used for incoming digital signals from a source and one twisted pair is used for outgoing digital signals back to the source. In addition, there are categories for classifying horizontal UTP cables and connecting hardware by performance capabilities. Thus, Category 3 encompasses UTP cables and connecting hardware with transmission characteristics up to 16 MHz, Category 4 encompasses UTP cables and connecting hardware with transmission characteristics up to 20 MHz and Category 5 encompasses cables and connecting hardware with transmission characteristics up to 100 MHz. 10BASE-T Ethernet (10 Mbs) can be implemented with Category 3, 4 or 5 cables and connecting hardware, whereas 100BASE-TX Fast Ethernet (100 Mbs) can be implemented with Category 5 cables and connecting hardware.
A need exists for a network interface device for interconnecting Ethernet networks which use unshielded twisted pair cables. A need also exists for a network interface device for interconnecting such Ethernet networks and for interconnecting telephone voice lines and coaxial cables. A need further exists for a network interface device for interconnecting Ethernet networks which use unshielded twisted pair cables and for interconnecting telephone voice lines and coaxial cables and which also provides overvoltage protection for the unshielded twisted pair cables, telephone lines and coaxial cables.
The present invention fills that need by providing a network interface device for interconnecting Ethernet networks which use unshielded twisted pair cables and for interconnecting telephone lines and coaxial cables while, at the same time, providing overvoltage protection for the unshielded twisted pair cables, telephone lines and coaxial cables.